Elma Instruments 5706445410286, Руководство пользователя

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Elma BM 251s-257s side 25
Crest Factor
Crest Factor is the ratio of the Crest (instantaneous peak) value to the True RMS value and is commonly
used to define the dynamic range of a True RMS DMM. A pure sinusoidal waveform has a Crest Factor
of 1.4. A badly distorted sinusoidal waveform normally has a much higher Crest Factor.
NMRR (Normal Mode Rejection Ratio)
NMRR is the DMM's ability to reject unwanted AC noise effect that can cause inaccurate DC
measurements. NMRR is typically specified in terms of dB (decibel). This series has a NMRR
specification of >60dB at 50 and 60Hz, which means a good ability to reject the effect of AC noise in DC
measurements.
CMRR (Common Mode Rejection Ratio)
Common mode voltage is voltage present on both the COM and VOLTAGE input terminals of a DMM,
with respect to ground. CMRR is the DMM's ability to reject common mode voltage effect that can cause
digit rolling or offset in voltage measurements. This series has a CMRR specifications of >60dB at DC to
60Hz in ACV function; and >120dB at DC, 50 and 60Hz in DCV function. If neither NMRR nor CMRR
specification is specified, a DMM's performance will be uncertain.
Operation
CAUTION
Before and after hazardous voltage measurements, test the voltage function on a known source such as
line voltage to determine proper meter functioning.
AutoCheckTM mode
This innovative AutoCheck
TM
feature automatically selects measurement function of DCV, ACV or
Resistance (

) based on the input via the test leads.
●With no input, the meter displays “Auto” when it is ready.
●With no voltage signal but a resistance below 10M

(nominal) is present, the meter displays the
resistance value. When the resistance is
below “Audible Threshold”, the meter further gives a continuity
beep tone.
●When a signal above the voltage threshold of 1V DC or AC up to the rated 1000V is present, the meter
displays the voltage value in appropriate DC or AC, whichever larger in peak magnitude.